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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 17 October 2011 by John Hartz

This is a reprint of a news release posted by the Cooperative Institute of Research in Envronmental Sciences (CIRES) of the University of Colorado at Boulder on Oct 11, 2011.

While climate change will not modify the extent or frequency of El Niño variability in the next 100 years, the environmental consequences of such events may become more extreme, according to a new collaborative study between scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the National Center for Atmospheric Research (NCAR).

Based on the latest state-of-the-art model, it does not appear that the warm water/cold water anomaly in the Pacific—known as El Niño and La Niña—is changing," said study coauthor Baylor Fox-Kemper, a CIRES Fellow and assistant professor at the Department of Atmospheric and Oceanic Sciences at the University of Colorado Boulder. "But due to a warmer and moister atmosphere the impacts of El Niño are changing even though El Niño itself doesn't change."

El Niño events—anomalous warming of the surface water of the eastern and central Pacific Ocean, occurring every four to 12 years—typically coincide with atmospheric changes like reduced trade winds and a displaced jet stream, which can cause unusual weather patterns such as flooding or droughts. These weather patterns can have dire consequences: "Tens of billions of dollars are associated with big El Niño events or La Niña events," Fox-Kemper said.

Advance knowledge of variations in El Niño behavior would allow a community to better prepare, for example, by altering planting seasons or water usage, Fox-Kemper said. "We would like to ask questions such as whether the flooding that occurred in Australia will happen more or less often over the next 100 years," he said. "If one of the impacts of climate change is a changing El Niño, we would like to know as soon as possible so we could start planning."

To determine whether El Niño may become stronger or more frequent in a warming climate, and whether the impacts of El Niño may change, the researchers used the most recent and advanced climate model available from NCAR—the latest version of the Community Climate System Model that scientists are using for the experiments that will inform the next Intergovernmental Panel on Climate Change (IPCC). They compared the model reproductions of variability in ocean surface temperature in the 20th century with model simulations that extended into the 21st century, and found that the changes were not significant. The study was published online in September in the Journal of Climate.

The impacts of El Niño, however, were affected by a warming climate, Fox-Kemper said. "What we see is that certain atmospheric patterns, such as the blocking high pressure south of Alaska typical of La Niña winters, strengthen in the model in the future climate as compared to the 20th century," he said. "So, the cooling of North America expected in a La Niña winter would be stronger in future climates."

Moreover, Fox-Kemper cautions that although El Niño does not appear to be changing in the short-term, it may change in the future under the influence of current climatic warming. Because the oceans heat up slowly and ocean currents move slowly there is a subsequent time lag before the tropics warm up. This means scientists will have to wait longer to see if there are any changes to El Niño with a changing climate, he said. "Even 100 years from now, ocean warming is still working its way through the system," he said. "This study isn't saying there isn't going to be a change to El Niño—it is just that the adjustment process is still happening."

The National Aeronautics and Space Administration, National Science Foundation, the US Department of Energy and the National Energy Research Scientific Computing Center provided funding for the study "Will there be a significant change to El Niño in the 21st century?" Lead author of the study is CIRES scientist Samantha Stevenson and coauthors on the study include NCAR researchers Markus Jochum, Richard Neale, Clara Deser and Gerald Meehl.

The following is NCAR's summary of the paper described above as posted on the Staff Notes webpage of NACAR on Oct 17. Note that NACAR chose a different headline for its summary.

El Niño and climate change in the coming century

Climate change is not expected to affect the extent or frequency of the El Niño/Southern Oscillation (ENSO) over the 21st century, but it could worsen its impacts. That’s the conclusion of a modeling study published in Journal of Climate in September.

ENSO events occur about every 4–12 years when surface waters warm anomalously in the tropical Pacific Ocean off the coast of South America. The phenomenon creates unusual weather patterns around the globe that can cause billions of dollars in damages from floods and droughts. Advance knowledge of ENSO’s behavior could help communities prepare for these catastrophes.

The research team, which was led by Samantha Stevenson (University of Colorado Boulder) and includes NCAR scientists Markus Jochum, Richard Neale, Clara Deser, and Gerald Meehl, used the NCAR-based Community Climate System Model (CCSM) to simulate the effects of climate change on ENSO over the 21st century. They found no significant changes in its extent or frequency.

However, the warmer and moister atmosphere of the future could make ENSO events more extreme. For example, the model predicts the blocking high pressure south of Alaska that often occurs during La Niña winters to strengthen under future atmospheric conditions, meaning that intrusions of Arctic air into North America typical of La Niña winters could be stronger in the future.

Comments

I'm not quite sure whether I have understood this correctly.
Are they saying that over the next 100 years the El Nino frequency and magnitude will remain about the same, but they don't rule out changes in the 22nd century?

My read is that they're saying that they aren't ruling out future changes to ENSO events at any time (10, 20, 50, 100 years or more). They are simply saying that ENSO does not appear to have changed/be changing as a result of climate change at this point in time (which is pretty early in the game).

What they are also saying, however, is that in spite of the fact that ENSO events are not changing, the far reaching impacts of those events are accentuated/worsened by the other changes that are taking place in the climate. So while the frequency and intensity of ENSO events are the same, how those events are impacting places like Australia, North America and South America is greater (possible/probable example: the current Texas drought).

Despite some claims about changes in ENSO patterns, no increase in frequency or magnitude can be attributed to AGW at this point, and unlikely in the near future. Both El NIno and La Nina events will occur as before, but changes in local impacts are possible.

Most observed changes in ENSO can be tied to changes in the PDO whereby alternating cycles of greater and more frequent El Ninos are followed by greater and more frequent La Ninas.

There is a strong correlation between the ENSO cycles and Arctic cloud formation. El Nino increases evaporation which leads to increased cloud formation, which results in warmer winters, but cooler summers, La Nina has the opposite effect. The timing of each is crucial as the possibility exists for both warmer winters and summers, cooler winters and summers, or one warm and one cool.

The other factor is the polar vertex. A strong polar vortex leads to reduced sea ice, while a weaker vortex induces sea ice growth.

This winter, we are headed towards a weak La Nina, with an expected strong polar vortex, which would result in reduced sea ice this winter.

"Unaffected by climate change" in the title doesn't make sense. I guess you are equating climate change to CO2. There are natural climate cycles which certainly drive el nino. One obvious driver is the 22 year and 172 year cycles of solar activity caused by the solar tidal effects of the nearby planets. Here is a paper discussing these effects which predicts a 30 year tendency towards la nina has just started.
http://multiscience.metapress.com/content/f524m4271487p0u2/?p=d0e5d392df674dd3afb4df2304b3f5e9&pi=9
More info at http://www.landscheidt.info/

tblakeslee, your links point to astrological theories about the movements of the planets causing solar cycles. Theodor Landscheidt for example had a book called "Sun, Earth, Man: A Mesh of Cosmic Oscillations - How Planets Regulate Solar Eruptions, Geomagnetic Storms, Conditions of Life and Economic Cycles". Those are the type of sources you think help your case? Really??

tblakeslee Do not assume that just because a paper has appeared in a journal that it is correct. Be skeptical of all you read. First see if the paper has been cited, and by whom and where. If a paper has been in print for a while (or is one of a sequence of papers along the same lines) but nobody is citing it (other than self-citations) then there is probably a good reason for it. Second ask where it was published, was it published somewhere it would get a competent peer review. Look at the lines of evidence cited in the paper and see if they pan out, follow the references and see what they say. One should always be especialy skeptical of papers that are contraversial, big claims require big evidence.

In this case, the paper cites the work of Friis-Christensen and Lassen (1991) on the link between solar-cycle length and northern hemisphere data. However, he doesn't cite the papers that show that the correllation was partially due to errors in the analysis and that as Lassen himself points out the correllation broke down soon after the Friss-Christensen paper was published. Now this was well known by the time Landscheidt wrote the paper, so you have to ask yourself (a) why he didn't mention this and (b) why the reviewers didn't pick it up if they were competent to review a paper on solar-climate links.

As has been demonstrated on other threads, the frequency and intensity of extreme weather events are on the rise and have been for 15 to 20 years.
As some of you have pointed out to me the cause of many of these events can just as likely be sheeted home to ENSO as they can be to AGW.

Can someone please help me out on this as I am getting a little confused?

How can we explain the increase of extreme weather events if ENSO has not noticably intensified, but the extra water vapour and energy in the atmosphere due to warming can also be put down to effects of ENSO?

Stevo, I think what you are missing is that a significant El Nino or La Nina represents a relatively extreme distribution of the energy in Earth's system. there's lots of heat in some places, less in others, some areas are particularly dry, others particularly wet. In a world with no warming trend, then extreme events related to heat, dry and wet might be expected to occur relatively more often when ENSO is at one particular end of its cycle, occasionally breaking records.

Add in a warming trend, and the extreme events still occur quite often at the endpoints of ENSO, due to the (heterogeneous?) distribution of energy about the earth, conducive to local extremes of weather. However, the extra energy, heat, evaporation, precipitable water etc that is a physical product of a warmer atmosphere means that the ENSO extremes are made even more extreme, and relatively more records tumble as a result.*

Not sure if that helps, but it's how I visualise it. For me, the increase in extremes are a product of global warming, but ENSO provides conditions in which you'll more likely see extremes.

*disclaimer, I'm not saying all extremes are a consequence of ENSO, or all ENSOs produce large extremes.

skywatcher, thankyou for your help.
"A warmer atmosphere means that the ENSO extremes are made even more extreme, and relatively more records tuble as a result."
Your disclaimer is also well noted.
From what I've seen in recent years the extremes are certainly becoming more extreme.
What are we looking for to be able to identify AGW as pushing these extremes?
Is it a matter of waiting until our data of recorded events extend for long enough to be statistically valid?

I'm not sure I'm the one to try and answer that question. Certainly there seems to be trends in extremes, whether in the oft-quoted trend in US daily record highs over daily record lows, or in Peterson et al 2008. The temperature patterns are consistent with AGW as a cause, ie a rise in maxima, a rise in minima, and in many cases minima rising faster than maxima (along with winters warming faster than summer, nights faster than days) - see the relevant threads on human fingerprints of AGW.

The following are ENSO plot for the past 130 years. The ENSO extremes have not changed during this timeframe. Oftentimes, it the timing of the ENSO events which have resulted in the extremes, rather than an extreme El Nino or La Nina.

The followign shows the US record highs and lows for the past century. The oft-quoted trend is prdominantly a result of much fewer lows. The highs have also decreased, but not nearly as much as the lows. As skywatcher mentioned, warmer winters and nights, but there has been no noticeable change in high temperatures.

http://www.worldclimatereport.com/index.php/2011/10/17/no-change-in-storminess/ It would appear your press release has been trumped by peer reviewed scientific literature that has studied storm intensity over the last 5000 years with no indication of major change in storm intensity or quantity!

a study of Holocene intense hurricane strikes in parts of the Gulf of Mexico (essentially local/regional conditions found during a time dissimilar to those expected during the 21st Century for the globe as a whole)

a study of extreme value statistics under modeled North Atlantic cyclones during winter conditions vs those in a warmer climate (again, a regional study; the primary finding was that in a warmer climate there was a more northern track followed by the cyclones; conclusions beyond that not possible due to the need for a larger sample size)

So you would have readers here believe that a study looking at past, localized conditions in the Gulf of Mexico and another study of North Atlantic cyclone extreme value statistics (both with afore-detailed limitations) rule out future, global expected changes as detailed in the OP. Seriously?

A prudent "skeptic" would take the time to actually read the referenced studies for themselves before swallowing disinformation hook, line and sinker.

What a bizarre site form which you've chosen to get "information." It doesn't allow comments. It claims to be "exhaustively researched, impeccably referenced" and yet I found wildly egregious errors in the first three posts I perused.

It also claims to be "acclaimed by those on both sides of the global warming debate," but I find that very hard to believe. It looks like just one more wildly wrong, Cato funded denial machine to me.

I would suggest that in the future you take a very skeptical eye to anything you see there... look for someone who has something else to say about it, and weigh the two positions before getting on board with take from the "World Climate Report."

[Actually, from what I can see you'd be better off just avoiding the site altogether, unless you enjoy being misinformed.]

Adrian, instead of referencing a propoganda piece, how about directly referencing the peer-reviewed research that backs your claim. Then we can have a serious look at it.
I wonder though. Would you continue to trust a source (eg Pat Michaels) even if shown to be producing disinformation? If you will uncritically accept information so long as it says what you want it to, then there is little point discussing points with you except to ensure others are not led astray.